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26.1.3.1.2 Method 2: Reduction of α-Diazo Ketones

DOI: 10.1055/sos-SD-026-00085

Yus, M.; Nájera, C.Science of Synthesis, (200526155.

The acidic decomposition of α-diazo ketones [‌14‌] can be used for the reduction of primary α-diazo ketones, such as compound 5, to methyl ketones 6 by means of 47% hydriodic acid[‌1‌] in chloroform at room temperature[‌15‌‌17‌] (Scheme 2). The accepted mechanism for this reaction involves the formation of a diazonium ion, which undergoes nucleophilic substitution with loss of nitrogen to give intermediate α-(iodomethyl) ketones.[‌14‌] Hydriodic acid can be replaced by potassium iodide and phosphoric acid, but lower yields are observed.[‌16‌] Starting from carboxylic acids, the corresponding diazo ketones are obtained through the reaction of diazomethane with their acyl chlorides.[‌18‌] Therefore, this is a mild two-step procedure for converting an acyl chloride into a methyl ketone. Condensation of 1,2-diketones with 4-toluenesulfonyl hydrazine at the less hindered side, followed by elimination of 4-toluenesulfinic acid upon adsorption on basic alumina is an alternative common methodology.[‌18‌] Freshly prepared solutions of metallocenes derived from titanium, zirconium, and niobium (prepared by reducing the corresponding metallocene dichlorides with 1 equivalent of magnesium under argon) reduce acyclic α-diazo ketones in very good yields (9095%).[‌19‌]

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Meeeeeeeeeeee ee eeee ee eeeeeee eeeeeeeeeee eee eeeeeeeeee eeee eeeee ee eee eeee ee eeeeeeeeeeeeeeeeeeee eee eeeeeeeeeeeeeeeeee[‌88‌] eeeeeee eeeeeeeeeee eeee Meeee eeeeeeeeeeeeee.[‌88‌] Meeeeeeeeeee-eeeeeeeeee eeeeeeeeee ee 8-eeeeeeeeeeeeeeee-8,8-eeeeee ee eeeeeeee eeeeeeee eeeeeee eeeeeeee eeeeee ee 8-eeeeeeeeeeeeeee-8,8-eeeeee.[‌88‌] Mee eeeeeeee eeeeeee ee eeeeeee eeeeeeeeeeeee eeeeee ee e eeeeeee eeeeeeeeeeee ee eee eeeeeeee-eeee eeeeeeee eeeeeeee.

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Meeeeeeeeeee Meeeeeeee

8,8-Meeeeeeeeeeeeee (8); Meeeeee Meeeeeeee:[‌88‌]

8,8-Mee(eeeeeeeeeeeeeeeeeee)eeeeeee (8; 88e, 88eeee, eeeeeeee eeee eeeeeeeeeeee eeee) eee eeeee eeeeee 8e ee e eeeeeeeeee eeeeeee eeeeeee ee MMMe8 (888eM) eee 88% MM (88eM). Meeee eeeeeeee eee ee eeeeeeeeee 88eee, M8M (888eM) eee eeeee. Mee MMMe8 eeeee, eeeeeeee eeee e MMMe8 eeeeeee ee eee eeeeeee eeeeee, eee eeeeee eeeeeeeeeeee eeee M8M, 88% Me8M8M8, M8M, eee. MeMMM8, eee MMe, eee eeeee. Meeee eeeeeeeeeee ee eee eeeeeee, eee eeeee eeeeeee eee eeeeeeee ee eeeeeeeeeeeeee [eeeeeee eeeeeeeeeee ee MeMMe, eeeeeeeee eeeee/eeeeeee (MMMMMMM: eeeeeeeeee) 8:8], eee eeeeeee eeeeeeeeeeeeeeeee (eeeeeeeee eeeee) eeee 8; eeeee: 8.88e (88%); ee 888°M.

8-Meeeeeeeee-8-eee (8); Meeeeee Meeeeeeee:[‌88‌]

Me e 888-eM, eeeee-eeeeee eeeee eeeeee eeee e eeeeeeee eeeeee, e eeeeeeeeeee, e eeeeee eeeeeeeee eeeeeeeee ee ee eeeeeeee, eee e eeeeeeee eeeeeeee eee, eee eeeeee MMe8 (8.88eM, 88eeee), MMM (88eM), eee M8M (8.8eM, 888eeee). Me eeee eeeeeee eeeeeee eee eeeee (eeee 8e) e eeee ee 8-eeeeeeeeee-8-eee (8.88e, 88.8eeee) ee MMM (88eM) ee 88°M. Meeee eeeeeeee eee ee eeeeeeeeee eeee ee eee eeee eeeeeeeeeee, M8 eeeeeeeee eee eeeeeeeeeeee. Mee eeeeeeeee eeeeeee eee eeeeeee eeee e 8M MeMMe eeee eee eeee 88% M8M8 (88eM), eeeeeeeeeee eee eeeeeeeeeee eeeee 88°M. Mee eeeeeee eeeee eee eeeeee eeee M8M eee eeeeeeeee eeee Me8M (8 × 88eM). Mee eeeeeeee eeeeeeee eeee eeeee (Me8MM8) eee eeeeeeeeee. Mee eeeeeeeee eee eee eeeeeeeee ee eeeeee 8; eeeee: 8.88e (88%); ee 88.888°M/8.88Meee.

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